This invention relates to an apparatus of cooling an electric motor that is used, for example, in aircraft applications.
In many motor applications significant cooling is required to maintain the motor within acceptable temperatures. An electric motor includes a fixed stator that rotationally drives a rotor. The stator is typically cooled by airflow through slots located at an outer diameter of the stator. The motor rotor is typically cooled by providing air to a gap, which separates the stator and rotor. Typically the air provided to the stator and rotor originates from the same source. Often high pressure cooled bleed air is used as the motor cooling source, which reduces engine performance.
The size of the gap between the stator and rotor affects the motor performance. The gap is minimized to provide better performance and efficiency for the motor. However, minimizing the gap restricts the flow of cooling air, which makes cooling the rotor more difficult. At high rotational speeds, the viscous forces between the stator and rotor create a high impedance at the gap. As a result, high pressure air is required to force the cooling flow through the gap. The cooling slots at the stator outer diameter, however, typically do not require this high pressure to force the cooling flow through the slots. As a result, the overall efficiency of the cooling arrangement suffers from providing unneeded high pressure air to the stator.
What is needed is a cooling arrangement that does not negatively impact the motor performance and efficiency nor overly burdens the cooling source.